From Low Fat to Low Carb: The Changing Face of Weight-Loss Advice

Hey it’s Sammy! 

Your Good Farm in-house nutritionist. Here to bring you essential information on nutrition, diet and permaculture gardening - in a bite size, easy to understand, science-backed way.

We’re up to part 2 on the Understanding Weight & Metabolic Health Series:

From Low Fat to Low Carb: The Changing Face of Weight-Loss Advice

Over the decades, weight-loss advice has shifted from one dietary rule to another. We've been told to cut fat, count calories, avoid carbohydrates, increase protein and, more recently, restrict the hours in which we eat.

Each approach has had its moment in the spotlight. But four things are worth keeping in mind: diet trends change, the fundamentals of good nutrition don't; food quality is often overlooked in favour of the latest dietary rule; and losing weight is not the same as keeping it off.

So, what has the research actually shown, and which approaches are worth holding on to?

The early days of dieting

In 1863, English undertaker William Banting published Letter on Corpulence, describing how he lost weight on a low-carbohydrate diet. He reduced foods such as bread, potatoes and sugar, while eating meat, fish and other animal foods. His approach became so popular that 'Banting' was used as a term for dieting.

By the twentieth century, calorie counting and portion control had become increasingly popular. Diet books, commercial programmes and meal replacements offered structured ways to reduce food intake. Weight loss became an increasingly commercial pursuit, with a growing market for products and programmes promising results.

Meanwhile, rates of overweight and obesity continued to rise. Australian data show that adult obesity increased substantially between 1980 and 2000, which doesn’t mean dieting advice caused the rise, but it does show that the strategies being promoted weren't reversing the broader trend.

The low-fat movement

From the 1950s onwards, dietary fat came under increasing scrutiny. Ancel Keys' diet-heart hypothesis proposed a link between saturated fat, blood cholesterol and heart disease. His influential Seven Countries Study helped establish this thinking, although the selection of countries and interpretation of the findings have since been questioned. Critics argue that the evidence was selectively interpreted and that public health recommendations to reduce dietary fat went further than the research justified.

Fat was also targeted for weight loss because it contains more than twice the energy per gram of protein or carbohydrate.

By 1982, advice to limit fat and eat more breads and cereals, vegetables and fruit had made its way into Australia's first Dietary Guidelines.

More than 40 years later, the five food groups remain the foundation of our national dietary advice, with grain-based foods still occupying a prominent place. The Australian Dietary Guidelines were last updated in 2013. Yes, you read that correctly. They are now under review by the NHMRC, with draft recommendations expected for public consultation in late 2026.

Food manufacturers quickly responded to the demand for low-fat options. Reduced-fat milk, low-fat yoghurt, spreads, dressings and 'lite' products filled supermarket shelves. In many cases, fat was replaced with sugar and refined starches to maintain taste and texture.

The message was simple: fat makes you fat, and low-fat is the healthier choice.

Over time, this blurred the distinction between different types and sources of dietary fat. Many people came to believe margarine was automatically healthier than butter, and that full-fat dairy should be avoided when trying to lose weight. These beliefs have been slow to shift. Learn more in our [fat series here].

Today, around two-thirds of Australian adults are living with overweight or obesity. While the overall proportion has stabilised in recent years, obesity rates have continued to rise, from 19% in 1995 to 33% in 2022–24.

Fat is an essential nutrient. It provides essential fatty acids, supports cell membranes and hormone production, helps the body absorb vitamins A, D, E and K, and contributes to satiety. The focus should not be on avoiding fat altogether, but on choosing quality sources and considering the overall diet.

From low carb to fasting

By the late 1990s and early 2000s, low-carbohydrate diets were back in the spotlight. The Atkins diet became hugely popular, followed by the South Beach diet and, more recently, ketogenic eating.

These diets challenged the low-fat message by reducing carbohydrates and increasing protein and fat. For some people, this can help manage hunger and reduce reliance on refined carbohydrates and sugary foods. However, restrictive approaches aren't necessary or suitable for everyone.

A major 2018 trial published in JAMA compared healthy low-fat and low-carbohydrate diets in 609 adults over 12 months. Participants lost an average of 5.3 kg on the low-fat diet and 6 kg on the low-carb diet. The difference was not statistically significant, suggesting neither approach was clearly superior. However, the study did not follow participants beyond the 12-month intervention, so it is unclear how much of the weight loss was maintained over the longer term.

Other trends followed, including Paleo, gluten-free eating, juice cleanses, meal replacements and intermittent fasting.

Paleo eating focuses on meat, fish, eggs, vegetables, fruit, nuts and seeds, while excluding grains, legumes and dairy. It can support weight loss for some people by reducing reliance on refined and processed foods and increasing protein and whole foods, which can help with fullness and appetite.

It can also serve as a short-term reset for people wanting to identify foods that may be contributing to digestive symptoms. A period of elimination followed by careful reintroduction can help assess individual tolerance. Grains and legumes are not inherently problematic for everyone, and traditional preparation methods such as soaking, sprouting and fermenting can improve their digestibility. 

Intermittent fasting gained mainstream attention through British doctor Michael Mosley. His 2012 BBC documentary Eat, Fast and Live Longer introduced many people to the idea that periods of controlled fasting might support weight management and metabolic health.

His 5:2 approach involved eating normally for five days a week and restricting intake to around 500 calories for women and 600 for men on the other two days. Interest extended beyond weight loss to research into calorie restriction, healthy ageing and metabolic markers.

Fasting can help some people reduce overall food intake. Research also suggests it can improve markers of metabolic health, including fasting insulin, insulin resistance and blood pressure. Some studies have also reported improvements in blood glucose and blood lipids. However, these benefits are not consistently greater than those achieved through other forms of calorie restriction.

Fasting isn't suitable for everyone. Factors such as stress, hormonal health, activity levels and nutritional needs need to be considered. The aim should be to support metabolic health without compromising adequate nourishment.

When nutrition becomes a marketing opportunity

Diet trends create commercial opportunities. When consumers are encouraged to avoid fat, manufacturers develop low-fat products. When carbohydrates become the enemy, low-carb breads, bars and snacks appear. When protein becomes the focus, everything from yoghurt to breakfast cereal starts carrying a high-protein claim.

Weight-loss programmes have followed a similar pattern. Jenny Craig and Lite n' Easy, for example, offer structured, portion-controlled meals designed to simplify food choices and manage energy intake. These programmes can help people lose weight, but maintaining results once the prepared meals and structure are removed can be more challenging.

A product can be low in fat, low in carbohydrates, high in protein or gluten-free and still be highly processed. A health claim on the front of a packet tells us little about its overall nutritional quality.

Health Star Ratings can also be misleading. Highly processed products can receive favourable ratings, giving consumers the impression that they are healthier choices. A star rating doesn't tell us enough about ingredient quality, the degree of processing or what has been added. Turn the packet over and read the ingredients. The list often tells us far more than the claims on the front.

Our Good Farm Good Guide has more on how to read food labels.

So, what is the most sustainable approach to weight loss?

One of the recurring patterns in weight-loss research is that losing weight is often easier than keeping it off. Weight regain is common, even after successful diet and weight-loss programmes. In a Melbourne trial, participants who lost at least 12.5% of their starting weight regained around 70% of that loss over the following three years, regardless of whether they lost it quickly or gradually.

Rather than following another diet trend, consider your individual health needs and build from a balanced, nutrient-dense approach to eating.

Food quality is fundamental to where we start. As discussed in our previous article, many ultra-processed foods are formulated to be highly palatable, combining ingredients, flavours and textures in ways that encourage us to eat more and come back for more.

In a controlled NIH study, participants ate around 500 calories more per day when offered an ultra-processed diet compared with a minimally processed diet, despite the diets being matched for several nutritional characteristics. This highlights how the degree of food processing can influence appetite and how much we eat.

The focus should be on getting the right balance of quality macronutrients, choosing whole-food sources and eating in a way that supports appetite, muscle and metabolic health.

Protein cannot be overlooked. Protein is the most satiating macronutrient. It helps keep us fuller for longer, reduces hunger and can reduce the urge to snack between meals. Include a good source at every main meal, such as eggs at breakfast, fish or meat at lunch, and legumes or other protein sources at dinner. (Shop our protein rich meals here)

Protein also helps preserve muscle during weight loss. Combined with resistance exercise, it supports muscle maintenance and growth. Muscle uses energy even at rest, so maintaining it helps support daily energy expenditure. This becomes increasingly important as we age.

Fibre supports digestive health, feeds beneficial gut bacteria and helps with fullness. Include vegetables, legumes, fruit, nuts, seeds and whole grains regularly.

Dietary fats provide essential fatty acids, support hormone production and help the body absorb vitamins A, D, E and K. They also contribute to satiety. Choose sources such as extra virgin olive oil, avocado, nuts, seeds and oily fish.

Carbohydrates have a place too. Choose whole-food sources such as vegetables, fruit, legumes and whole grains rather than relying heavily on refined flour, sugary drinks and packaged snacks. Pairing carbohydrates with protein, fibre and fat can slow digestion and moderate the rise in blood glucose after eating.

The balance will vary between individuals. Some people feel better eating fewer carbohydrates, while others do well with more. The aim is to find an approach that provides adequate nourishment, supports appetite and muscle, and is realistic to maintain. Not a one-size-fits-all diet or the latest trend, but an approach that works for your individual needs.

Weight loss should not come at the expense of nutrition. The goal is to lose excess body fat while keeping the body well nourished, strong and metabolically healthy.

In our next article, we'll look beyond diet at some of the other factors that can influence weight management, including thyroid function, insulin resistance, metabolic set point and meal timing.

References

Banting, W. (1863). Letter on Corpulence, Addressed to the Public. London.

Gabel, K. & Varady, K.A. (2022). Current research: effect of time restricted eating on weight and cardiometabolic health. The Journal of Physiology, 600(6), 1313–1326.

Gardner, C.D., Trepanowski, J.F., Del Gobbo, L.C., et al. (2018). Effect of low-fat vs low-carbohydrate diet on 12-month weight loss in overweight adults: The DIETFITS randomized clinical trial. JAMA, 319(7), 667–679.

Garegnani, L.I., Oltra, G., Ivaldi, D., et al. (2026). Intermittent fasting for adults with overweight or obesity. Cochrane Database of Systematic Reviews, Issue 2, CD015610.

National Health and Medical Research Council (NHMRC). (2013). Australian Dietary Guidelines. Canberra: NHMRC.

National Health and Medical Research Council (NHMRC). (2013). Australian Dietary Guidelines: Appendix C – History and timeline of Australian nutrition documents. Canberra: NHMRC.

Australian Institute of Health and Welfare (AIHW). (2026). Overweight and obesity. Canberra: AIHW.

Purcell, K., Sumithran, P., Prendergast, L.A., Bouniu, C.J., Delbridge, E. & Proietto, J. (2014). The effect of rate of weight loss on long-term weight management: A randomised controlled trial. The Lancet Diabetes & Endocrinology, 2(12), 954–962.

Varady, K.A., Cienfuegos, S., Ezpeleta, M. & Gabel, K. (2021). Cardiometabolic benefits of intermittent fasting. Annual Review of Nutrition, 41, 333–361.

Varady, K.A., Cienfuegos, S., Ezpeleta, M. & Gabel, K. (2022). Clinical application of intermittent fasting for weight loss: Progress and future directions. Nature Reviews Endocrinology, 18, 309–321.

Klein, A.V. & Kiat, H. (2015). Detox diets for toxin elimination and weight management: A critical review of the evidence. Journal of Human Nutrition and Dietetics, 28(6), 675–686.

National Health and Medical Research Council (NHMRC). (2006). Nutrient Reference Values for Australia and New Zealand Including Recommended Dietary Intakes. Canberra: NHMRC.

Jäger, R., Kerksick, C.M., Campbell, B.I., et al. (2017). International Society of Sports Nutrition position stand: Protein and exercise. Journal of the International Society of Sports Nutrition, 14, 20.

Food Standards Australia New Zealand (FSANZ). Health Star Rating System: How ratings are calculated.